• Luigi Vivona, Robert Huhle, Anja Braune, Martin Scharffenberg, Jakob Wittenstein, Thomas Kiss, Michael Kircher, Paul Herzog, Moritz Herzog, Marco Millone, Gama de AbreuMarceloM, and Thomas Bluth.
• From the Department of Anesthesiology and Intensive Care Medicine, Pulmonary Engineering Group, University Hospital Carl Gustav Carus at the Technische Universität Dresden, Dresden, Germany (LV, RH, AB, MS, JW, TK, PH, MH, MM, MGA, TB), Department of Pathophysiology and Transplantation, University of Milan, Italy (LV), Institute of Nuclear Medicine, University Hospital Carl Gustav Carus, Dresden (AB), Department of Anesthesiology, Elblandklinikum Radebeul, Radebeul (TK), Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe (MK), Drägerwerk AG & Co KGaA, Lübeck, Germany (MK), IRCCS San Martino IST, Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy (MM), Department of Intensive Care and Resuscitation (MGA) and Department of Outcomes Research, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, USA (MGA).
• Eur J Anaesthesiol. 2023 Jul 1; 40 (7): 501510501-510.

BackgroundVariable ventilation recruits alveoli in atelectatic lungs, but it is unknown how it compares with conventional recruitment manoeuvres.ObjectivesTo test whether mechanical ventilation with variable tidal volumes and conventional recruitment manoeuvres have comparable effects on lung function.DesignRandomised crossover study.SettingUniversity hospital research facility.AnimalsEleven juvenile mechanically ventilated pigs with atelectasis created by saline lung lavage.InterventionsLung recruitment was performed using two strategies, both with an individualised optimal positive-end expiratory pressure (PEEP) associated with the best respiratory system elastance during a decremental PEEP trial: conventional recruitment manoeuvres (stepwise increase of PEEP) in pressure-controlled mode) followed by 50 min of volume-controlled ventilation (VCV) with constant tidal volume, and variable ventilation, consisting of 50 min of VCV with random variation in tidal volume.Main Outcome MeasuresBefore and 50 min after each recruitment manoeuvre strategy, lung aeration was assessed by computed tomography, and relative lung perfusion and ventilation (0% = dorsal, 100% = ventral) were determined by electrical impedance tomography.ResultsAfter 50 min, variable ventilation and stepwise recruitment manoeuvres decreased the relative mass of poorly and nonaerated lung tissue (percent lung mass: 35.3 ± 6.2 versus 34.2 ± 6.6, P  = 0.303); reduced poorly aerated lung mass compared with baseline (-3.5 ± 4.0%, P  = 0.016, and -5.2 ± 2.8%, P  < 0.001, respectively), and reduced nonaerated lung mass compared with baseline (-7.2 ± 2.5%, P  < 0.001; and -4.7 ± 2.8%, P  < 0.001 respectively), while the distribution of relative perfusion was barely affected (variable ventilation: -0.8 ± 1.1%, P  = 0.044; stepwise recruitment manoeuvres: -0.4 ± 0.9%, P  = 0.167). Compared with baseline, variable ventilation and stepwise recruitment manoeuvres increased Pa O 2 (172 ± 85mmHg, P  = 0.001; and 213 ± 73 mmHg, P  < 0.001, respectively), reduced Pa CO 2 (-9.6 ± 8.1 mmHg, P  = 0.003; and -6.7 ± 4.6 mmHg, P  < 0.001, respectively), and decreased elastance (-11.4 ± 6.3 cmH 2 O, P  < 0.001; and -14.1 ± 3.3 cmH 2 O, P  < 0.001, respectively). Mean arterial pressure decreased during stepwise recruitment manoeuvres (-24 ± 8 mmHg, P  = 0.006), but not variable ventilation.ConclusionIn this model of lung atelectasis, variable ventilation and stepwise recruitment manoeuvres effectively recruited lungs, but only variable ventilation did not adversely affect haemodynamics.Trial RegistrationThis study was registered and approved by Landesdirektion Dresden, Germany (DD24-5131/354/64).Copyright © 2023 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.

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